Chemistry: Crude oils and fuels

Separating crude oil

Crude oil is a mixture of hydrocarbons and it can be used to produce many useful materials. It can be separated into different fractions using fractional distillation and some of these can be used as fuels. 

Crude oil forms naturally over millions of years from the remains of living things. Most of the compounds in crude oil are hydrocarbons which are compounds that contain hydrogen and carbons only, joined together by bonds called covalent bonds. 

There are different kinds of hydrocarbons but most in crude oil are alkanes. 

The alkanes are a family of hydrocarbons and share the same general formula: C_nH_2n+2

Distillation separates a pure liquid from a mixture of liquid. It works when the liquids have different boiling points. 

The mixture is heated in a flask. Ethanol has a lower boiling point than water so it separates first. The ethanol vapour is then cooled and condensed inside the condenser to form a pure liquid. The thermometer shows the boiling point of the pure ethanol liquid. When all the ethanol has evaporated from the solution, the temperature rises and the water evaporates. 

Heating --> Evaporating --> Cooling --> Condensing

Fractional distillation is a different type of distillation because it separates a mixture into a number of different parts (fractions). A tall column is fitted about the mixture with several condensers coming off at different heights. The column is hot at the bottom and cool at the top…